Rework CTSM so that parameters can come in easily with different dimensionality: scalar, by-PFT, by gridcell, by-gridcell-and-PFT

[ekluzek]

An idea from @dlawrenncar from the LMWG meeting today, is to be able to easily try an experiment where a parameter comes in with a different dimensionality than is hardcoded in the parameter file. And specifically to allow a parameter to come in as a map by gridcell. With that it seems like you might as well allow it by gridcell and PFT as well. This would be something that would be experimental and just allow you to easily try different dimensionalities for Perturbed Parameter Ensemble (PPE) type experiments. Or just for work with specific parameters. With experimentation the default parameter might be tuned to work with a specific dimensionality, and kept at the level for future default work.

[ekluzek]

@katiedagon @djk2120 @adrifoster and others working in the PPE space, how useful does this all sound for your work? Especially my addition I added above where I go beyond @dlawrenncar suggestion so that the map is dimensioned by PFT? I also generalized his request so that dimensionality could be easily moved between any dimensionality (including scalar and by PFT)

[adrifoster]

This would be very useful! But in terms of time scale of usage I'm not sure . For my part I think it might be a future need rather than a short-term one. I will let others chime in on when they might be interested in using this

[ekluzek]

This would definitely have to be post CESM3. But, it would be good to gauge how soon after CESM3 it would be useful to bring in.

[linniahawkins]

Echoing Adrianna, the PPE posse (thanks Rosie) is definitely interested in this capability. It would open up alternative calibration methods (e.g., CARDAMOM) and enable new science questions (what can we learn from emergent gradients of 'optimal' parameter settings?). Matt Williams gave a presentation at the ILMF parameter estimation webinar that highlights some of the scientific value of this capability. Recording here.

[ekluzek]

OK, looking at how parameters are handled now, I think there would need to be some redesign brought in to make this easy and flexible.

There's paramUtilMod.F90 that is sometimes used to read in parameters of different dimensions. It recognizes the dimension level, and can read in scalar, 1D, or 2D level variables. Only FATES uses it for beyond scalar's. And it's not used consistently in the code.

readParams calls all the subroutines that reads in parameters for different physics packages. Each package has their list of variables and dimensionality explicitly defined as native FORTRAN types.

[ekluzek]

Using paramUtilMod consistently in the code seems to me as a good first step. Another part of that would be to have a parameter type that can be of different dimensionality and the user can choose at run time what that dimensionality of each variable would be.

[ekluzek]

One way to do this would be to have four different parameter files. One for pure scalars, one for PFT, a streams file by gridcell, a 3D streams file by gridcell and PFT. The user then moves variables to the other file to change the dimension.

I suspect this might NOT be liked by scientists though, so maybe there is one file and you change the dimension of the variables on the file? Going from 1D to 2D seems like a big shift to me though. So maybe there has to be two one for scalar and by-PFT, and another for stream files of either 2D or 3D?

Thoughts on this idea?

[ekluzek]

I'm thinking the way to go about this would be to figure out a design to work towards, and then take small refactoring steps toward the full design. The first steps wouldn't add new functionality and only do some refactoring to make future steps easier. Later steps would start to allow flexibility between scalar and by-PFT. Then an extension for 2D and 3D maps on the model resolution. And then an extension for 2D streams would be a later step, with the possibility of adding 3D streams later.

I'm thinking we'd use OO classes to have a Base parameter class, a scalar class, a by-PFT class, a 2D fixed resolution class, a 3D fixed resolution class, a 2D stream class, and then a 3D stream class. There would need to be some infrastructure for it to decide what dimensionality each parameter actually is. I think it would just read in the different files and use the dimension from the file it's on, and only fail if it can't find a parameter on any of the files.

[glemieux]

Another clarifying question @ekluzek: is there any particular benefit (aside from code reuse, which to be clear is important) in CTSM reading in netcdf file formats? I'm assuming there is a performance and portability benefit over reading in human-readable formats.

I ask as I'm wondering if there is a case to be made for facilitating @rgknox suggestion through the development of intermediate tooling that could be both user-facing as well as callable during the build process? Perhaps it could align with work towards #2126 (and maybe even #585)? But maybe this my question is getting out of scope of this issue.

[ekluzek]

This is a good question and something I was going to ask as well. Way back we decided at one point to move ALL scalar parameters to the namelist, and leave the netCDF parameter file for parameters by PFT. But, the feedback from scientists at the time was that is was easier to have everything on one netCDF file. So then we made efforts to move scalar parameters back to the netCDF file. So now nearly everything is on the same netCDF file (both scalar and by-PFT). We also thought that with 78 PFT's it was better to have this in netCDF over having long lists in for example namelist format.

One thing we thought of in the context of #585 that you point out above is that we thought we'd have an ASCII interface for users to modify the values in the parameter file. So it would be something like a user_nl_clm_params file that works similarly to user_nl_clm for example. We'd probably have it in a more advanced config file format (YAML, paramGen, JSON, XML etc.). Then CTSM would take that file and modify the parameter file accordingly and write it out in netCDF for you. And we'd probably have a mode where you could use the user defined netCDF parameter file as well. This might be getting at what you saying above @glemieux and @rgknox.

But, yes @adrifoster @linniahawkins @katiedagon @djk2120 and anyone else -- is it still desirable to have ALL parameters on the same netCDF file? And do you have a preferred format for parameters?

[ekluzek]

@billsacks has a comment in the above issue that outlines some of the thinking we had about this.

#585 (comment)

@billsacks when you have a chance if you could chime in one what you remember about some of this that would be great.

[rosiealice]

All parameters in the same format is v. much more useful than having them spread across different formats for the (pleasingly) expanding PPE posse.

78 parameter long lists seem to store neatly in netcdf but maybe there are other formats where it wouldn't be super awful? Idk...

Having the means to easily script modifications to the parameter files, e.g. using python is quite critical. Can one do that with xml?

I find that having the default parameter file as part of the fates codebase (admittedly as a .cdl) is VERY very useful from a development and communication perspective.

Unsure where the Venn diagram intersects here, but that's my feedback anyway. :)

[glemieux]

@rosiealice Ryan has facilitated this for the fates parameters with the UpdateParamAPI python script with the use of the xml "patch" files (example).

@ekluzek yep, that's what I was thinking. Thanks for the fleshing out background info on this subject!

[dlawrenncar]

I think the hydrology community would be very interested in this. Not having this capability is actually deterring use by some on the hydrology community, as far as I understand. And, we saw the example this week about how it could likely be possibly useful for the crop model, essentially accounting for different crop varieties. Dave

…

On Thu, Feb 29, 2024 at 10:34 AM Erik Kluzek ***@***.***> wrote: @adrifoster <https://github.com/adrifoster> @samsrabin <https://github.com/samsrabin> @slevis-lmwg <https://github.com/slevis-lmwg> @glemieux <https://github.com/glemieux> and @rgknox <https://github.com/rgknox> do you have thoughts on this as it's the more SE oriented issue. — Reply to this email directly, view it on GitHub <#2395 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AFABYVEQJP42LUDX6TOOAZDYV5TBHAVCNFSM6AAAAABEAI4CXWVHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4DMMZUGAYDA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[rosiealice]

Just a +1 from me on what Dave said. I have had several conversations in the not so distant past with people interested in this type of thing. (Mortality rates, leaf reflectance, whatever). Though it further muddies the water on what a parameter is etc. (feel sure there is a musical context I could put that in, but I can't quite grasp it...)

[ekluzek]

@adrifoster pointed out to me that the same species of an evergreen tree lives in Mexico and Alaska, but acts a lot different. So the parameters should really be different for it by region. I'll let her add to this but that makes sense to me for a reason for this to happen.

[adrifoster]

not the same species of tree, but the same PFT! And the "same" species of tree ( specifically I was talking about AK birch vs. paper birch) lives in Alaska (AK birch) and also across Canada (paper birch). We can make those different species (they are really sub-species) but where do we draw the line between the two ranges? At the Alaska-Canada border? I have never heard of trees obeying border control.

So essentially allowing for geographical variance of parameters would allow us to actually simulate a gradation between AK birch and paper birch.

[samsrabin]

@ekluzek I think what you wrote in terms of incremental development makes a lot of sense, as does extending paramUtilMod. As @rosiealice mentioned, it's starting to blur the lines between what's a parameter and what's just a regular model input. I could imagine a "parameter" like crop maturity requirements that's 4D: latitude, longitude, CFT, and time. I don't think that's necessarily a bad thing, though.

One thing I'd like us to shoot for is to avoid having to write much new code whenever a new parameter is added. The more we can make this automatic, the better.

[ekluzek]

One thing I'd like us to shoot for is to avoid having to write much new code whenever a new parameter is added. The more we can make this automatic, the better.

Exactly that's one of the important design requirements we want to do as well as we can. Part of my idea of having a parameter type that has different classes, is so the dimensionality of the parameter is NOT known to the code outside of the parameter class. That way the parameter can be defined with any dimensionality by the user based on the input files, and the code just does the right thing based on what you give it.

Another design consideration though is going to make sure this doesn't make the code dog slow. Depending on how we design the accessors to the parameter data there could be a slow down. But, I also think that some slow down might be worth it for the flexibility it gives scientists in experimentation and using ML in fitting parameters.

[samsrabin]

This might be a separate discussion, but it's been nagging at me and seems relevant here.

Lots of crop development ideas (e.g., having one patch in a corn/soy rotation, or ) either require (a) rethinking how we handle about CFTs/patches or (b) making new CFTs. The latter is more realistic given engineering resource constraints, but it's currently a pain to make new CFTs. Each requires a new integer identifier like nirrig_rice to be defined and used in various places. It's also error-prone and annoying on principle to have to mess around with code just because you want to add a new CFT.

We should make this a lot more flexible. PFTs should be defined—not just parameterized, but defined—in model inputs, not the code itself.

This would require changing everything that uses PFT identifiers (e.g., nirrig_rice, nbrdlf_evr_shrub, etc.) to instead use new PFT-specific parameters. However, in addition to easing the introduction of new PFTs, it would make the code a lot safer—resolving this long-standing issue for instance.

[rosiealice]

@samsrabin noting that lots of this would be easier in. FATES, which has neither of the issues (patch/PFT correspondence being definitive, nor inflexible pft definitions. You are right it is a bigger/different discussion though!

[ekluzek]

Yep, you are definitely correct here @samsrabin. That is totally something that would really help to work on. A nice thing about FATES for example is that the FATES parameter file does define your PFT's so it's easy to change them. The CTSM parameter file also has an assumed order that trees are first, shrubs next, grasses next, and then crops. I think the code will abort if you get this wrong, but you have to create parameter files with that ordering. And that means you can't do the simple thing of adding a new PFT at the end of the file for example (unless it's a crop). So it does really limit the science that can be done in CTSM. And it's both a bad software design as well as limiting the science, so bad from all angles.

Basically you are advocating for a data driven approach rather than a code driven approach which is far easier to understand as you point out. It's easier for everyone to understand what the code is doing by just looking at the input files.

In terms of this initial idea and in terms of software I would call this a separate discussion. But, I could also see where this effort could grow into that space. With the idea that you don't know what dimensionality a parameter is -- you have to access it via an accessor method. So you have to pass in the indices you want. Initially you'd have to pass in those PFT identifiers (just because that's what the current code looks like). But, eventually that parameter reading class could take over what pftconMod.F90 does and have ways of querying the parameter object to do everything in pftconMod (is_tree, is_shrub, etc.). I think that makes sense as a way to go. And we might as well think about the initial design to at least assess if that makes sense as something to do eventually. So there is a reason to talk about this here.